1. Field of the Invention
This invention relates generally to building block components for use in high performance programmable digital systems, and in particular to an arithmetic logic register stack integrated onto a single semiconductor chip.
2. Prior Art
In the past, digital systems have been fabricated from a multiplicity of logic circuits such as AND or OR gates, flip-flops, and the like. From one to four such logic circuits are integrated onto a single semiconductor chip. These logic circuits are commonly referred to in the art as small scale integration. Numerous small scale integrated logic circuits are assembled onto a board containing printed circuit interconnections between each of the individual logic circuits, and numerous such assembled boards are electrically interconnected for constructing programmable digital systems. These digital systems have disadvantages of being large in size, requiring large amounts of power for operation, and are relatively slow in operation due to the physical distance between components.
More recently, typical circuits frequently employed in constructing digital systems have been integrated onto a single chip thereby mitigating somewhat the above-described disadvantages. One such example of such a typical integrated circuit is a multiplexer.
With recent improvements in integrated circuit technology, a still larger number of circuit components can be integrated onto a single semiconductor chip. Thus, larger portions of digital systems can be combined onto a single semiconductor chip. However, this improvement in the integrated circuit art has brought about different types of problems. For example, integrated circuits for digital systems were custom made for different applications, and the cost for such custom-made circuits is prohibitive. Also, with a larger number of circuits on a single semiconductor chip, a concomitant increase in the number of pin connections to the integrated circuit were required.